The present invention relates to silicone emulsions and more particularly the present invention relates to silicone emulsions for rendering silicate particulate matter such as perlite and vermiculite water-resistant. Perlite and vermiculite are naturally occurring siliceous rock. Perlite is a volcanic glassy ash rock while vermiculite is mica.
The distinguishing feature which sets perlite and vermiculite apart from other mineral glasses is when they are heated to a suitable point in their softening range, these rocks expand to 4 to 20 times their original volume. This expansion is due to the presence of two to six percent by weight of combined water in the crude perlite or vermiculite rock. When such ground crude perlite or vermiculite rock is heated to a temperature above 1600.degree. F. or 871.degree. C., the crude rock rapidly expands in a manner similar to popcorn as the combined water vaporizes and creates countless tiny bubbles in the heat softened glassy particles. It is these tiny glass-sealed bubbles which account for the very light weight and other exceptional physical properties of expanded perlite or vermiculite.
Expanded perlite and vermiculite can be manufactured to weigh as little as two pounds per cubic foot or 32 kilograms per cubic meter making such expanded perlite and vermiculite adaptable for numerous industrial uses. Accordingly, such material as perlite and vermiculite and specifically the expanded perlite has countless uses as additives in the formulation of abrasives, acoustical plaster, acoustical tile, charcoal barbecue base, concrete aggregate, filteraid, fertilizer extender, foundry ladle covers, foundry sand additive, inert carrier, insulation board, loose fill insulation, packaging material, paint texture, pipe insulation, plaster aggregate, plaster texture, potting soil additives, soil conditioner, tile mortar aggregate and wallboard core filler.
In the loose fill application for instance, it may be inserted into hollow masonry cavities such as that in concrete blocks or between brick walls and other masonry walls as insulation. It has been found it can also be incorporated in the formulation of insulation boards and other types of wall materials for insulative properties. It has been found that when perlite has been used as loose fill insulation in masonry walls, it has retarded the passage of heat or of cold through the wall by 50%.
Accordingly, perlite and vermiculite as an insulation have found wide acceptance in the building industry. However, there is one difficulty with perlite and vermiculite as insulation. Due to the large surface area of the particulate matter after it has expanded it will absorb and hold a great deal of moisture. Thus, expanded perlite or expanded vermiculite when manufactured is completely dry, but when exposed to moisture it will pick up 50% of the exposed moisture and absorb it.
The perlite or vermiculate that has absorbed moisture also tends to keep the moisture in the perlite or vermiculite particle. Such perlite or vermiculite particulate matter when it has become saturated with moisture functions ineffectively and very poorly as a thermal insulation barrier. Accordingly, it was highly desirable to make expanded perlite or expanded vermiculite resistant to the adsorption of water vapor. There are a number of coatings that could be utilized to make vermiculite and perlite resistant to water vapor, however, silicones is one of the basic chemicals in industry that has resistance to weathering and specifically, water vapor. Silicone solutions for application to masonry walls so as to render them water repellent are well known. Accordingly, it was highly desirable to formulate a silicone coating solution or material for application to perlite or vermiculite so as to render it water resistant. Accordingly, various silicone compositions were formulated for this application. One such silicone composition for application to perlite to render it water repellent is an emulsion of a methyl hydrogen polysiloxane fluid.
It should be noted to maintain the cost of the treated perlite as inexpensive as possible, it was desirable to apply the silicone coating to the perlite in as inexpensive a manner as possible. Accordingly, one process which has been devised and which has been found highly suitable is to produce a solution of emulsion of the silicone and spray it on the heated perlite as it comes from the furnace.
Accordingly, the water in the water emulsion then is evaporated and the silicone is cured onto the perlite. This is a simple and inexpensive way of applying the silicone coating. Accordingly, it was highly desirable to formulate silicone coatings, which could be applied by a simple spray method onto the expanded perlite or expanded vermiculite. Accordingly, the water emulsions of methyl hydrogen polysiloxane fluid could be applied in such a manner. However, the trouble with such emulsions and specifically with methyl hydrogen polysiloxane fluids, is that they will slowly at times liberate hydrogen upon standing in the 55 gallon drums in which they are packaged. Accordingly, the drums have to be continually checked to see that the hydrogen gas is released to the atmosphere and does not accumulate in the drum and possibly result in a fire or explosion.
Another type of silicone composition which was found acceptable for coating expanded perlite or expanded vermiculite is an aqueous solution of sodium methyl siliconate. Sodium methyl siliconate is a water repellent compound which when applied to masonry will render it water repellent. The difficulty with such sodium methyl siliconate is that it is corrosive and, accordingly, has to be handled carefully by the workers applying the material and handling it.
Another type of silicone that could be utilized is an alkoxy functional silane such as methyltrimethoxy silane dissolved in water or as a dispersion in water. The difficulty with such alkoxy silanes is that unless they are dispersed to quite a low concentration in water they are highly flammable materials since the pure material has a flash point of 47.degree. F. Accordingly, all the prior art silicone coatings for silicate particulate matter were found to be undesirable for one reason of another and basically because of flammability or handling problems. Accordingly, it was highly desirable to find a silicone material or a silicone coating composition which would coat the silicate particulate matter such as expanded perlite or expanded vermiculite and which was not flammable and which was not dangerous to handle by the workers applying the compositions in the field.
It was also desirable to prepare a silicone coating composition which could be applied with facility to the expanded perlite and vermiculite as the expanded perlite and vermiculite were manufactured in the factory or plant in which they were produced.
It should be noted that in the above description while in some sense specific to expanded perlite and expanded vermiculite applies to other particulate silicate matter. There are other types of particulate silicate matter which is desired to be made water-resistant by applying a silicone coating thereover. That the prior art silicone compositions which could be applied to such particulate silicate matter to make it water resistant have the disadvantages discussed previously. Accordingly, it was highly desirable to be able to formulate a suitable silicone coating for all types of silicate particulate matter including perlite and vermiculite. It is one object of the present invention to provide for a silicone coating for a silicate particulate matter which is inexpensive, and simple to apply. It is another object of the present invention to provide for a silicone coating composition for expanded perlite and vermiculite which is inexpensive and simple to apply.
It is an additional object of the present invention to provide for silicone coating compositions for perlite and vermiculite which coating compositions are not flammable.
It is yet an additional object of the present invention to provide for a simple and economic silicone coating emulsion composition for perlite and vermiculite which does not present a problem in handling by the workers applying the composition. These and other objects accomplished by means of the disclosure set forth hereinbelow.